There are many ways to transport both people and goods, including airplanes, automobiles, and trains. The length of time that a trip may take is often a determining factor for the type of transportation that may be used, and there is a demand for shorter travel times between destinations. In addition to travel time, many consumers choose their method of transportation based on cost and consumers will often choose one airline carrier over another based on ticket price. The efficiency of a method of transportation plays a big role on costs passed on to consumers. For instance, when the price of aviation fuel increases, some airlines also increase the cost of tickets. Additionally, consumers are more environmentally conscious and are looking to alternative energy modes of transportation when making their transportation decisions.
Business travelers are primarily concerned with speed, and automobiles are not the first choice for long distance travel. Such consumers really have only one travel option: flying. The speed of commercial aircraft, however, is practically limited by the speed of sound, because as an airplane speeds up and begins to approach the speed of sound, it enters a speed region known as the transonic region. When the airplane enters the transonic region, parts of the airflow over the airplane's surface are subsonic and parts are supersonic. Air is strongly compressible near the speed of sound and the supersonic parts emanate shock waves that are approximately normal to the surface of the airplane. The shock waves increase drag (wave drag) and decrease lift. Thus, as the speed of the aircraft varies as it accelerates through the transonic region, movement of the waves on the surface causes buffeting. The wave drag gives rise to a power peak at Mach 1 called the “sound barrier.” After the airplane passes through the transonic region, the stability of the vehicle improves and the power requirement drops temporarily below the power peak of the sound barrier. Nonetheless, the power continues to rise with speed and, due to wave drag, is much higher than at subsonic speeds. Indeed, the power in the supersonic region rises at more than the third-power of speed. The additional power requirements make supersonic airplanes prohibitively expensive to build and operate, especially for commercial use. This means that in order to increase their speed past the speed of sound, aircraft must use significantly more fuel, charge higher prices for either passengers or cargo in order to make up for the increases in fuel usage, and will expel more emissions into the environment.
The foregoing examples of the related art and limitations therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.